The aim of this proposal is to develop quantitative indices of regional left ventricular performance derived from the gated equilibrium radionuclide ventriculogram, and based on changing regional count rates rather than on geometric techniques borrowed from contrast ventriculography. We will first validate regional ejection fraction as a quantitative index of regional left ventricular performance. We will then assess the significance of temporal as well as spatial alterations in segmental left ventricular performance, and determine their reliability as markers of reversible left ventricular asynergy. The natural history of regional left ventricular performance in acute myocardial infarction will be determined, as well as the potential modification of segmental wall motion by pharmacologic interventions. We plan to measure regional ejection fraction to evaluate the effects of manipulations of systemic and coronary vascular tone on regional wall motion. The approach that we propose to develop would provide a non-invasive reproducible method for the serial evaluation of left ventricular function. It will enable us to investigate objectively and quantitatively questions which currently may be answered only by invasive radiologic techniques. In addition to providing a better understanding of the control of coronary vascular tone and the factors responsible for the precipitation of myocardial ischemia, the technique provides a potential approach for the objective diagnosis and assessment of coronary artery disease and an objective method for the determination of the efficacy of medical managements aimed at the treatment of that disease.